[clang-tools-extra] [clang-tidy][NFC] Clarify some options use regex to matching in doc (1/N) (PR #161142)

[Victor Chernyakin via cfe-commits]

================
@@ -39,8 +39,8 @@ Options
 
 .. option:: ExcludeClasses
 
-    Semicolon-delimited list of class names for overwriting the default
-    exclusion list. The default is:
+    Semicolon-delimited list of regular expressions matching class names that
+    overwriting the default exclusion list. The default is:
----------------
localspook wrote:

```suggestion
    overwrites the default exclusion list. The default is:
```

https://github.com/llvm/llvm-project/pull/161142